This invention relates to apparatus and methods for operating chucks of rotary power tools and particularly to keyless operation of drill chucks and the like.
Rotary tools are commonly used to perform various operations such as drilling, screwing, sanding and the like. Rotary tools are used not only by professional amateur craftsmen but also by orthopedic surgeons in operations such as installing artificial hip joints and bone screws. In orthopedic surgical procedures, it is often necessary to drill into a bone and tap threads into it so that the bone will retain a threaded skew or the like therein.
A typical rotary tool includes an electric or fluid motor unit mounted within a housing having a handle with a built in trigger switch for controlling the motor speed. A drive shaft projects forward from the motor and housing to carry a chuck assembly. The chuck assembly typically includes a chuck locking drum cylinder and a chuck inner cylinder. The inner cylinder is threadedly received on the drive shaft, and the locking drum cylinder is mounted concentric to the inner cylinder. The chuck jaws are threadedly engaged in the locking drum and are opened or closed in response to the locking drum being driven clockwise or counterclockwise relative to the shaft. Shafts of rotary tool implements such as drills, screwdrivers and the like include shank portions that are designed to be gripped by the chuck jaws. A typical chuck jaw structure is adjusted to receive differently sized tool shafts by turning the locking drum via a bevel gear positioned on a forward edge of the locking drum. The chuck jaws are manually opened or closed with the aid of a chuck key.
The use of a chuck key to open or close the chuck jaws has several disadvantages. The chuck key is easily misplaced or lost, which can cause problems particularly in surgical uses of rotary tools. Considerable time may be wasted in changing tools in the chuck jaws.
Their are several keyless chuck gripping devices known in the art, but they have several disadvantages and have received little or no commercial acceptance. Previous keyless chuck gripping devices are difficult to install on an existing chuck, provide insufficient torque and friction to tighten the chuck jaws sufficiently to retain a tool shaft therein, and are difficult to manufacture and save little or no time over the use of a conventional chuck key.